1. Technical Field
The apparatus and method of the present invention relate generally to aircraft altitude monitoring for small, general aviation aircraft. More specifically, they relate to an apparatus and method of providing automatic monitoring of the aircraft's present altitude, and issuance of alert warnings, upon detection of deviations from a target altitude, to the pilot.
Pilots are frequently given instructions from Air Traffic Controllers (ATC) in rapid fire sequence. Consequently, pilots have developed several techniques to remind them of these instructions. For example, it is common to use the autopilot heading bug on the heading indicator as a reminder of an assigned heading. The present invention described herein provides a reminder of altitude assignments, and an alerting mechanism to warn of excursions from an assigned altitude.
Most large and medium sized aircraft have on-board altitude alerting systems. In fact, The FAA mandates altitude alerting systems for jet aircraft. However, most smaller aircraft do not have this type of equipment. The main reason for this is cost, both of the equipment itself and also its installation. While altitude alerting systems are not routinely found in smaller aircraft, they are equally useful there. The present invention is designed to address these limitations and make alerters more widely available to small general aviation aircraft.
The present invention is adapted primarily to visually and/or aurally warn the pilot of altitude deviations from an assigned or desired altitude. The invention, in one design of the preferred embodiments, is designed to be self-contained so as to negate or minimize any installation work. Alternative designs of the preferred embodiments provide for acquisition of altitude information from external sources either as the primary altitude information source or as an alternate source. One example of such an external source is the GPS receivers, especially the hand held units which many pilots carry with them. The various designs may also be capable of alerting to the existence of other conditions such as abnormal vertical speeds and the like.
Two preferred embodiments are disclosed. The first preferred embodiment is a more sophisticated system providing a means wherein the target altitude may be preselected and will utilize a means for displaying information such as sensed system altitude. Further, the first preferred embodiment provides a means for calibrating the system altitude. The second preferred embodiment is a simpler system not utilizing a display or altitude preselect. Rather, this embodiment utilizes a simple push-button to designate the target altitude once the pilot has reached this altitude, thereafter, monitoring for any deviations therefrom.
The preferred embodiments comprise a plurality of designs utilizing a variety of sources of altitude information. In one design a self-contained altitude sensing means is used, eliminating the need to connect the alerter to the aircraft altimeter or encoder. In an alternative design, the altitude data from a Global Positioning System receiver may be used. In yet another design, the output of an altitude encoder may be used. Finally, various combinations of these sources may be utilized, cross-checking and verifying the altitude information between them.
In the designs utilizing a self-contained altitude sensing means, the alerter is able to utilize cabin pressure for altitude measurements since the pressure in an unpressurized aircraft cabin is approximately equal to that outside the aircraft. In fact this is the system utilized for alternate static source in most small aircraft. Any differences between the interior and exterior pressure are accommodated in the first preferred embodiment using the system calibration feature, and in the second preferred embodiment by use of relative pressure differences between the target and actual altitudes to determine alerts.
It is anticipated that the information displayed in the first preferred embodiment would utilize a multi-digit LCD to display the system altitude. The display may also be capable of displaying altitude deviations and other alpha/numeric data depending on the specific display means being used. Additionally, in both embodiments, an indicator light may be used to visually indicate excessive altitude deviations, vertical speeds, etc. Finally, aural warnings may be given either in the form of horns/beeps/synthesized voice which would coincide with the alert warning.
Throughout the specification, the following terms and their definitions will be used. "Present", "sensed", or "system" altitude will all be used to refer to the aircraft's altitude as read or computed by the altitude alerter. "Target" altitude will describe the desired altitude, i.e. the altitude the aircraft has been assigned, or the altitude that the pilot is otherwise wanting to maintain. The tolerance window is a number of feet, within which the aircraft altitude is allowed to deviate before triggering an alert. "Excessive deviation" will be used to refer to the situation where the absolute difference between the system altitude and the target altitude is greater than a tolerance window. Detection of an excessive deviation will result in an "altitude alert" condition.
It is envisioned that the present invention will be primarily designed for the enroute phase of the flight. Limitations in accuracy of the present invention does not permit its use in instrument approaches, or other phases of flight where great precision is required.
2. Description of the Prior Art
The concept of altitude alerting is not new. As mentioned above, turbine aircraft have been required to carry such equipment for some time. Additionally, there are several types of altitude alerting products currently on the market for smaller general aviation aircraft. However, these devices all suffer from drawbacks of one type or another which the present invention is designed to address.
By far the simplest and cheapest of the prior art alerters are the suction cup "bugs" adapted for placement on the altimeter window. These consist generally of some type of a rotatable arm which is placed at the desired setting. The theory being that the pilot will note when the altimeter hand is not co-located with the alert indicator, signalling an altitude deviation. The problem with such indicators is that there is also no automatic notification of an altitude alert. Thus, the pilot must be looking at the altimeter to see the warning. Consequently, there is no automatic safety alert of altitude deviation if a pilot is temporarily distracted from monitoring that specific instrument.
Other more complex prior art systems exist for monitoring altitude. These systems can be broken into two groups, differentiated primarily on the source of the altitude information.
The first group comprises alerters utilizing an altitude encoder, sometimes referred to as a "blind" encoder. As is well understood by those in the art, the FAA requires aircraft flying in certain airspace to have a "Mode C" altitude reporting transponder. The transponder usually receives its altitude information from this blind encoder. The blind encoder puts out a signal commonly referred to as a "grey code" representing the aircraft altitude which the transponder reads and transmits. The altitude alerters in this group also read this grey code and utilize that information for alerting purposes. There are several examples of such alerters on the market. Two examples of this type of prior art system are the Shaidan AMS 2000 and the Iccarus Instruments "AltAlert".
A second group of prior art systems use the aircraft's own Mode C transponder signal to display altitude information. This second group of altitude alerting systems receives the aircraft transponder's 1090 MHz RF transmission and displays the altitude information in the cockpit. Of course, the reliability of this type of system hinges not only on the encoder feeding the altitude information to the transponder, but also on the transponder itself. Unfortunately, the failure of the encoder or transponder is the time you most need an altitude altering system since ATC will no longer be able to provide the pilot with altitude deviation warnings. One example of this type of system is the Airsport Company's "Airsport PRO".
Finally, several manufacturers' products have an altitude alerter as a subsystem in another component. For example, the Bendix/King and S-TEC companies have such units. The S-Tec "Altitude Selector/Alerter" unit being part of an altitude preselect for its autopilot. This unit is also dependant on the aircraft encoder for the altitude information.
Finally, at least one autopilot utilizes a pressure transducer as part of its "altitude hold" function. However, there is no attempt to determine the actual altitude. Rather, the pressure sensor is simply used to keep the aircraft at the same pressure (altitude)without regard for what the altitude actually is. Additionally, there is no alerting capability.
As mentioned, one design of the altitude alerter of the present invention is adapted to be as self-contained as possible, eliminating any necessity for connection or reliance on an aircraft altitude encoding system, allowing it to be completely transportable.
To achieve this objective, the alerter of this design has been developed utilizing a self-contained source for altitude information. One example of such a self contained source is a pressure transducer. There are many examples of sensors which have acceptable pressure and voltage output ranges.
Consequently, it is a primary objective of the present invention to provide an altitude alerting apparatus and method using self-contained source of altitude information.
Another primary objective is to provide an alerter capable of reading altitude data from a pressure transducer.
An alternative objective is to build an alerter capable of reading altitude information from an altitude encoder.
Another objective is to provide an alerter apparatus capable of reading the altitude information from a Global Positioning System receiver, such as from an RS232 port.
It is a further objective of the present invention to provide an altitude alerting apparatus and method having an altitude range corresponding approximately to the most commonly used general aviation altitudes.
It is a further objective to provide a first preferred embodiment of an altitude alerting apparatus and method having a display means for displaying altitude information.
It is a further objective to provide a first preferred embodiment of an altitude alerting apparatus and method having a means for entering pre-selected target altitude information.
It is a further objective to provide a first preferred embodiment of an altitude alerting apparatus and method having a means for calibrating the system altitude.
It is a further objective to provide an altitude alerting apparatus and method having a means for visually signalling an altitude alert condition.
It is a further objective to provide an altitude alerting apparatus and method having a means for aurally signalling an altitude alert condition.
It is a further objective to provide an altitude alerting apparatus and method having a means for selecting an altitude deviation tolerance window, within which the aircraft altitude may vary without triggering an altitude alert warning.
It is a further objective to provide an altitude alerting apparatus and method having a means for indicating the present altitude as the target altitude.
It is a further objective to provide a first preferred embodiment of an altitude alerting apparatus and method having a means for providing a continuous visual display of the target altitude.
A final objective is to provide a simplified, second preferred embodiment having the minimum of components necessary to effect an altitude deviation detection and warning.